The present invention is in the field of retroviral vectors for gene therapy.
Recent progress in human genetics, especially in human genome research and gene transfer techniques, has brought gene therapy closer to clinical reality. Experimental human gene therapy has enjoyed some successes in the treatment of genetic defects, including adenosine deaminase deficiency, (Blaese R M, et al. Sciene 1995; 270: 470-474; Blaese R M, et al. Hum Gene Ther 1990; 1: 327-329, Bordignon C, et al. Science 1995; 270: 470-474) familial hypercholesterolemia, (Grossman M, et al. Nature Genet 1994; 6: 335-341) hemophilia, (Chuah M K L, et al. Hum Gene Ther 1995, 6: 1363-1377) and cystic fibrosis, (Colledge W H, et al. Brit Med Bull 1995; 51: 82-90) and acquired diseases such as cancer (Blaese R M, et al. Cancer Gene Ther 1995; 2: 291-297), heart disease (Smith L C, et al. Adv Exp Med Biol 1995; 369: 77-88), kidney disease (Smith L C, et al. Adv Exp Med Biol 1995; 369: 77-88), and acquired immunodeficiency syndrome (Yu M, et al. Gene Ther 1994; 1: 13-26).
At present, the primary limitation in the use of gene therapy to treat human disease is the ineffectiveness of gene delivery methods. Among several types of gene delivery systems for human gene therapy in clinical trials, Moloney murine leukemia virus (MLV) based vectors are the most widely used (Afione S A, et al. Clin Pharmacokinet 1995; 28: 181-189; Morgan R A, et al. Annu Rev Biochem 1993; 62: 191-217; Smith A E. Annu Rev Microbiol 1995; 49: 807-838, Vile R G, et al. Brit Med Bull 1995; 51: 12-30). MLV-based vectors offer highly efficient chromosome integration; thus, the therapeutic genes are transmitted to the progeny cells. However, MLV-based gene delivery methods are largely limited to ex vivo protocols, (Blaese R M, et al. Science 1995; 270: 470-474; Blaese R M, et al. Hum Gene Ther 1990; 1: 327-329; Bordignon C, et al. Science 1995; 270: 470-474; Grossman M, et al. Nature Genet 1994; 6: 335-341; Chuah M K L, et al. Hum Gene Ther 1995; 6: 1363-1377) in which the target cells are removed from the patient to receive therapeutic genes from the MLV vectors in vitro. Then the transduced cells are selected, expanded and reimplanted in the patient. The ex vivo procedure is cumbersome and costly, and in most cases, it can transduce only a small fraction of the target cell population (Rettinger S D, et al. Proc Natl Acad Sci USA 1994; 91: 1460-1464; Salmons B, et al. Leukemia 1995; 1: S53-S60). More efficient gene delivery protocols need to be developed, for advancing gene therapy to routine clinical practice.
In vivo gene transfer is conceptually attractive and potentially can be more efficient than the ex vivo procedure. However, due to limited titer (Vile R G, et al. Brit Med Bull 1995; 51: 12-30) and short half life at body temperature, direct administration of retroviral vectors into patients is limited in its applicability. Another alternative is to introduce producer cells directly into patients. In this scenario, gene transfer may continue in vivo for the duration of the life span of the implanted producer cells. Gene therapy using MLV-based producer cells to treat brain tumors (Culver K W, et al. Science 1992; 256: 1550-1552) has been carried out in clinical trials, but no clear clinical benefit has been reported Murine producer cells are rapidly inactivated in human serum, (Rother R P, et al J Exp Med 1995; 182: 1345-1355; Welsh R M, et al. Nature 1975; 257:612-614) thus, the lack of success in this case is not surprising. Implanting established human producer cell lines, however, risks the introduction of malignancy to the recipient. For these reasons, the conversion of human primary cells into producer cells has been proposed (Welsh R M, et al. Human serum lyses RNA tumor viruses. Nature 1975; 257:612-614). The primary cell-converted "producer cells" do not have the drawbacks discussed above yet they have the advantages of in vivo gene delivery.
Accordingly it is an object of the present invention to provide a method for gene delivery